Sealing structure for first stage stator blade of gas turbine

ABSTRACT

A gas turbine first-stage stator blade sealing structure for preventing the sealing air from leaking from the inside even if the blade falls or inclines due to thermal stress. A rear flange (12) of a first-stage stator blade (31) is formed in an arcuate shape having a straight rib (10). A stator blade support ring (13) contacts the straight rib (10) to form a sealing face. When the rear flange (12) and the stator blade support ring (13) fall or incline relative to each other due to thermal stress during operation, the upper end or lower end of the rib (10) contacts linearly with the face of the stator blade support ring (13) so that no clearance is established to inhibit leakage of the sealing air. In the prior art, where the horizontal rib (10) is absent, an arcuate clearance is established between the stator blade support ring (13) and the rear flange (12) as the support ring (13) inclines, and thus sealing air is allowed to leak from the inside to the gas passages.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a gas turbine first-stage stator bladesealing structure in which leakage of air is reduced at the stator bladeof a gas turbine.

2. Description of Related Art

FIG. 10 is a general section showing an arrangement of the blades of agas turbine. As shown, reference numeral 31 designates a first-stagestator blade, the rear flange 32 of which is fixed in contact with astator blade support ring 33 arranged in an arcuate shape around therotor. A plurality of stator blades 31 are arranged in contact with thestator blade support ring 33 around the rotor. Numeral 34 designates aplurality of first-stage moving blades which are arranged on a rotordisc adjacent to the stator blades 31 so that they rotate together withthe rotor. Similarly, numeral 35 designates a second-stage stator blade;numeral 36 designates a second-stage moving blade; numeral 37 designatesa third-stage stator blade; numeral 38 designates a third-stage movingblade; numeral 39 designates a fourth-stage stator blade; and numeral 40designates a fourth-stage moving blade. What is shown is an example of afour-stage gas turbine which has the stator blades and the moving bladesalternately arranged so that the moving blades are rotated by the hotcombustion gas.

FIG. 8 is a diagram showing the details of the first-stage stator blade31, the rear flange 32 and the stator blade support ring 33 thus fardescribed. While the gas turbine is being run, the stator blade supportring 33 is heated and thermally deformed due to the hot working gas suchthat the rear flange 32 and the stator blade support ring 33 moverelative to each other thereby causing a fall, as shown. Then, thecontacting faces partially lose contact with each other, as will bedescribed, to make the inner seal of the first-stage stator blade 31insufficient so that the sealing air 40 leaks.

FIG. 9 is a view taken in the direction of arrows IX--IX of FIG. 8. Therear flange 32 is arcuate along the stator blade support ring 33. Therear flange 32 and the support ring 33 are in contact with each other inthe normal state. Since the stator blade support ring 33 is alsocircular, however, a crescent clearance is established, as shown, whenthe blade relative to the ring falls. This clearance is leakage area 41,through which the sealing air leaks to thereby increasing the flow ofleaking air.

In the first-stage stator blade of the prior art gas turbine, asdescribed hereinbefore, when the rear flange 32 of the stator blade 31and the stator blade support ring 33 fall relative to each other due tothe thermal stress during the operation of the turbine, there isestablished between the contacting faces of the two a clearance, throughwhich the inside sealing air leaks so as to increase the leakage air.The leakage air is uselessly released to the combustion gas therebydeteriorating the performance of the gas turbine. Therefore, it has beendesired to improve the sealing structure of especially the first-stagestator blade.

SUMMARY OF THE INVENTION

Therefore, a fundamental object of the present invention is to provide agas turbine first-stage stator blade sealing structure in which thestructure of the contacting portions of the flange of a first-stagestator blade and the stator blade support ring is constructed so as toeliminate the aforementioned leakage of sealing air so that no clearancecan be established between the contacting faces of the ring and theflange even if they incline relative to each other due to the thermalstress, thereby preventing the sealing air from leaking from the insideto the outside.

In order to achieve the above-specified object, according to the presentinvention, the following two means (1) and (2) are provided.

(1) A gas turbine first-stage stator blade sealing structure comprising:a stator blade support ring arranged around a rotor; and a flange havingan arcuate side face contacting the circumferential side face of thestator blade support ring and fixing a stator blade. A straight ridge isformed on the arcuate side face of the flange and is held in contactwith the side face of the stator blade support ring.

(2) A gas turbine first-stage stator blade sealing structure comprising:a stator blade support ring arranged around a rotor; and a flange havingan arcuate side face contacting the circumferential side face of thestator blade support ring and fixing a stator blade. The flange ispartially cut away straight at its two arcuate lower end portions so asto contact the stator blade support ring. Also, the stator blade supportring is partially cut away straight at its circumferential end portionsso as to contact the flange side face.

According to the means (1) of the present invention, when the statorblade flange and the stator blade support ring deform relative to eachother due to thermal deformation during the operation of the gas turbineso that the blade inclines, the side face of the stator blade supportring is in contact with the upper end or lower end of the ridge, and theridge is straight, although the flange of the stator blade is arcuate,so that it maintains a linear contact with the side face of the statorblade support ring, and thus, no clearance is established. As a result,the sealing faces can be retained without any leakage of sealing airfrom the inside of the first-stage stator blade. In the prior art, thetwo side faces of the arcuate flange and the circular stator bladesupport ring are in direct contact so that the arcuate clearance isestablished at the contacting portions, when the two incline relative toeach other, thereby causing leakage of the sealing air. According to themeans (1) of the invention, however, that clearance is not establishedso that the air leakage can be prevented.

According to the means (2) of the invention, when the stator bladeflange and the stator blade support ring deform relative to each otherdue to the thermal deformation during the operation of the gas turbineso that the blade inclines, the two flange end portions and the statorblade support ring circumferential end portions are partially cut awaystraight at their portions in order to contact each other. As a result,even if the side face of the stator blade support ring inclines eitherforward or backward with respect to the flange, a straight line ofcontact is maintained between the upper end portion of the side face andthe side face of the flange or between the side face of the stator bladesupport ring and the cut away upper end portion of the flange, and thus,no clearance is established. Like the aforementioned means (1) of thepresent invention, it is possible to prevent leakage of the sealing airfrom the inside of the first-stage stator blade.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevation of a gas turbine first-stage stator bladesealing structure according to a first embodiment of the invention;

FIG. 2 is a view taken in the direction of arrows II--II of FIG. 1;

FIG. 3 is a side elevation showing the gas turbine first-stage statorblade sealing structure according to the first embodiment of theinvention and explains the action of the same;

FIG. 4 is a side elevation of a gas turbine first-stage stator bladesealing structure according to a second embodiment of the invention;

FIG. 5 is a view taken in the direction of arrows V--V of FIG. 4;

FIG. 6 is a view taken in the direction of arrows VI--VI of FIG. 4;

FIG. 7 is a side elevation showing the gas turbine first-stage statorblade sealing structure according to the second embodiment of theinvention and explains the action of the same;

FIG. 8 is a side elevation of a prior art gas turbine first-stage statorblade sealing structure;

FIG. 9 is a view taken in the direction of arrows IX--IX of FIG. 8; and

FIG. 10 is a side elevation of the inside of a prior art gas turbine.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be specifically described withreference to the accompanying drawings. FIG. 1 is a side elevation of agas turbine first-stage stator blade sealing structure according to afirst embodiment of the invention, and FIG. 2 is a view taken in thedirection of arrows II--II of FIG. 1. In these two figures, a rearflange 12 of a first-stage stator blade 31 is formed in an arcuate shapealong the circular shape of a stator blade support ring 13 and isprovided on its side face with a straight rib 10.

The rib 10 is formed so as to be straight on the arcuate rear flange 12,as shown in FIG. 2, and its thickness t is determined depending upon therelative blade fall due to the thermal deformation between the rearflange 12 and the stator blade support ring 13. In this embodiment, thethickness t is set at about 2 mm and may be at least about 2 mmconsidering the maximum fall due to the thermal deformation. The statorblade support ring 13 contacts the straight rib 10 to retain thehorizontal sealing face 10a of the rib 10.

FIG. 3 is a diagram showing a case in which a relative fall occurs dueto the thermal stress between the rear flange 12 and the stator bladesupport ring 13 in the sealing structure of the first embodiment. Asshown in broken lines, the stator blade support ring 13 is relativelyinclined leftward, as indicated by 13a, or rightward, as indicated by13b. Even if the stator blade support ring 13 is inclined, as indicatedby 13a or 13b, it still maintains contact with the upper end or lowerend of the rib 10. In this case, the rib 10 is mounted straight, asshown in FIG. 2, so that the sealing face 10a and the stator bladesupport ring 13 are held in straight or linear contact along ahorizontal line to maintain the seal without developing any clearance.

FIG. 4 is a side elevation of a gas turbine first-stage stator bladesealing structure according to a second embodiment of the invention;FIG. 5 is a view taken in the direction of arrows V--V of FIG. 4; andFIG. 6 is a view taken in the direction of arrows VI--VI of FIG. 4. Inthe second embodiment, as shown in FIG. 4, a rear flange 22 is cut awayso as to abut against the lower end portion of a stator blade supportring 23, thereby forming relief portions 25. These relief portions 25are formed by cutting away the lower end portions of the two sides ofthe arcuate rear flange 22, as shown in FIG. 5.

FIG. 6 is a view of the stator blade support ring 23, as taken in thedirection of arrows VI--VI. The circumferential end of the circularsupport ring 23 are cut away so as to abut against the rear flange 22 ofthe stator blade 31, and to form relief portions 24. Thus, the reliefportions 24 are formed in the stator blade support ring 23 whereas therelief portions 25 are formed in the rear flange 22, so that the contactof the sealing face is maintained even when the rear flange 22 and thestator blade support ring 23 fall relative to each other, as will bedescribed hereinafter.

FIG. 7 shows the sealing structure of the second embodiment of theinvention, in which the rear flange 22 and the stator blade support ring23 fall relative each other due to the thermal stress. When the statorblade support ring inclines leftward, as indicated by broken lines 23a,its relief portions 24 abut against the rear flange 22. These reliefportions 24 are formed straight, as shown in FIGS. 5 and 6, and theirabutting portions contact straight closely with the central portion ofthe face of the arcuate rear flange 22 so that the sealing face isretained with no clearance.

When the stator blade support ring 23 inclines rightward, as indicatedby dotted lines 23b in FIG. 7, the central portion of the stator bladesupport ring 23 contacts linearly with the rear flange 22, as shown inFIG. 5, while avoiding the relief portions 25 at the two end portions,so that an arcuate leakage area 41, such as that shown in FIG. 9, is notformed. As a result, no clearance is formed between the stator bladesupport ring 23 and the rear flange 22, and thereby the sealing face ismaintained.

According to the first and second embodiments thus far described, thereis adopted either the sealing structure, in which the rear flange 12 ismade by forming the straight rib 10 on the rear flange of the statorblade 31, or the sealing structure in which the rear flange 22 havingthe relief portions 25 and the stator blade support ring 23 having therelief portions 24 are combined. As a result, even if the first-stagestator blade 31 relatively falls or inclines due to the thermal stress,the sealing face can be reliably maintained without any clearancedeveloping on the contacting faces thereby preventing the sealing airfrom leaking from the inside.

What is claimed is:
 1. A gas turbine first-stage stator blade sealingstructure comprising:a rotor; a stator blade support ring arrangedaround said rotor; and a stator blade including a flange having anarcuate side face contacting a circumferential side face of said statorblade support ring, said flange having a straight ridge formed on thearcuate side face of said flange, and is held in contact with thecircumferential side face of said stator blade support ring.
 2. A gasturbine first-stage stator blade sealing structure comprising:a statorblade; a stator blade support ring arranged around a rotor and having acircumferential side face; and a flange connected to said stator bladeand having an arcuate side face contacting the circumferential side faceof said stator blade support ring, said flange being partially cut awaystraight at two arcuate lower end portions of said flange in order tocontact said stator blade support ring, wherein said stator bladesupport ring is partially cut away straight at circumferential endportions thereof to permit contact with said arcuate side face of saidflange.
 3. A gas turbine first-stage stator blade sealing structure asclaimed in claim 2, wherein said stator blade support ring is positionedrelative to said flange so that the cut away portions of said statorblade support ring contact a central portion of the arcuate side face ofsaid flange upon tilting of said stator blade support ring relative tosaid flange.
 4. A gas turbine first-stage stator blade sealing structureas claimed in claim 2, wherein the cut away portions of said statorblade support ring are spaced along the perimeter of said stator bladesupport ring.